This invention relates to improved molten metal spray forming and, more particularly, to gas flow and temperature control in metal spray forming for more uniform microstructure in deposited metal from the metal spray.
One example of generating a molten metal spray in combination with a molten metal refining process is disclosed and described in U.S. Pat. No. 5,160,532--Benz et al assigned to the same assignee as the present invention. In the noted patent, a metal melting and refining apparatus provides a pool of molten refined metal. A small diameter molten metal stream from the pool is caused to flow through a molten metal atomization ring manifold in which a row of gas orifices generate plural converging gas streams from a gas in the manifold which impact the passing metal stream to convert the stream to a spray or plume of small molten metal droplets. The metal spray is directed to and deposited on a collector surface to generate a billet or other spray formed object.
When the noted process is employed to generate very large metal billets by sweeping or scanning the spray over the collector surface, it has been noted that some nonuniform microstructures appear in the final product due to large radial temperature distributions in the deposited metal. Metal billets of low thermal conductivity metal alloys such as nickel (ni) based super alloys including IN718 and Rene 95 appear to be particularly affected by this problem and it is an object of this invention to provide means to control temperature distribution in molten metal sprays to minimize non-uniform microstructures in spray deposited metal objects.